The publications and other materials used herein to illuminate the background of the invention, and in particular, cases to provide additional details respecting the practice, are incorporated by reference.
Mammalian 17β-hydroxysteroid dehydrogenases (17β-HSDs) are NAD(H) or NADP(H) dependent enzymes which convert inactive 17-keto-steroids into their active 17β-hydroxy-forms or catalyse the oxidation of the 17β-hydroxy-forms into the 17-keto-steroids. Because both estrogens and androgens have the highest affinity for their receptors in the 17β-hydroxy form, 17β-HSD enzymes play an essential role in the tissue-selective regulation of the activity of sex steroid hormones. At present, 10 human members of the 17β-HSD enzyme family have been described (types 1-5, 7, 8, 10-12), whereby each type of 17β-HSD has a selective substrate affinity, directional (reductive or oxidative) activity in intact cells, and a particular tissue distribution.
Due to their essential role in the tissue-selective regulation of the activity of sex steroid hormones, 17β-HSDs can be involved in the occurrence and development of estrogen-sensitive pathologies (f. ex. breast, ovarian, and endometrium cancers etc.) and androgen-sensitive pathologies (f. ex. prostate cancer, benign prostatic hyperplasia, acne, hirsutism, etc). Furthermore, many types of 17β-HSD have been shown to be involved in the pathogenesis of particular human disorders such as pseudohermaphroditism (17β-HSD3), polycystic kidney disease (17β-HSD8) and bifunctional enzyme deficiency (17β-HSD4) [reviewed by: Mindnich et al (2004)]. Therefore treatment of sex steroid-sensitive diseases by administration of specific inhibitors of the 17β-HSDs enzymes have been suggested, optionally in combination with potent and specific anti-estrogens and anti-androgens [Labrie et al. (1997)].
The best characterized member of the 17β-HSD family is the 17β-HSD1 [EC 1.1.1.62]. The 17β-HSD1 enzyme catalyzes in vitro the reduction and the oxidation between estrone (E1) and estradiol (E2). However, under physiological in vivo conditions the enzyme only catalyses the reductive reaction from the estrone (E1) to the estradiol (E2). The 17β-HSD1 was found to be expressed in a variety of hormone-dependent tissues, e.g. placenta, mammary gland tissue or uterus and endometrium tissue, respectively.
Estradiol itself is, especially in comparison to the significantly less active estrone, a very potent hormone, which regulates the expression of a variety of genes by binding to the nuclear estrogen receptor and plays an essential role in the proliferation and differentiation of the target cell. Physiological as well as pathological cell proliferations can be estradiol dependent. Especially many breast cancer cells are stimulated by a locally raised estradiol concentration. Furthermore, the occurrence or course of benign pathologies such as endometriosis, uterine leiomyomas (fibroids or myomas), adenomyosis, menorrhagia, metrorrhagia and dysmenorrhoea is dependent from the existence of significantly high estradiol levels.
Endometriosis is a well-known gynaecological disorder that affects 10 to 15% of women in the reproductive age. It is a benign disease defined as the presence of viable endometrial gland and stroma cells outside the uterine cavity. It is most frequently found in the pelvic area. In women developing endometriosis, the endometrial cells entering the peritoneal cavity by retrograde menstruation (the most likely mechanism) have the capacity to adhere to and invade the peritoneal lining, and are then able to implant and grow. The implants respond to steroid hormones of the menstrual cycle in a similar way as the endometrium in the uterus. The infiltrating lesions and the blood from these lesions which are unable to leave the body cause inflammation of the surrounding tissue. The most common symptoms of endometriosis are dysmenorrhoea, dyspareunia and (chronic) abdominal pain. The occurrence of these symptoms is not related to the extent of the lesions. Some women with severe endometriosis are asymptomatic, while women with mild endometriosis may have severe pain. Up to now, no reliable non-invasive test is available to diagnose endometriosis. Laparoscopy has to be performed to diagnose the disease. Endometriosis is classified according to the 4 stages set up by the American Fertility Society (AFS). Stage I corresponds to minimal disease while stage IV is severe, depending on the location and the extent of the endometriosis. Endometriosis is found in up to 50% of the women with infertility. However, currently no causal relation has been proven between mild endometriosis and infertility. Moderate to severe endometriosis can cause tubal damage and adhesions leading to infertility. The aims of treatment of endometriosis are pain relief, resolution of the endometriotic tissue and restoration of fertility (if desired). The two common treatments are surgery or anti-inflammatory and/or hormonal therapy or a combination thereof.
Uterine leiomyomas (fibroids or myomas), benign clonal tumours, arise from smooth muscle cells of the human uterus. They are clinically apparent in up to 25% of women and are the single, most common indication for hysterectomy. They cause significant morbidity, including prolonged and heavy menstrual bleeding, pelvic pressure and pain, urinary problems, and, in rare cases, reproductive dysfunction. Myomas are found submucosally (beneath the endometrium), intramurally (within the myometrium) and subserosally (projecting out of the serosal compartment of the uterus), but mostly are mixed forms of these 3 different types. The presence of estrogen receptors in leiomyoma cells has been studied by Tamaya et al. [Tamaya et al. (1985)]. They have shown that the ratios of estrogen receptor compared to progesterone and androgen receptor levels were higher in leiomyomas than in the corresponding normal myometrium. Surgery has long been the main treatment for myomas. Furthermore, medical therapies that have been proposed to treat myomas include administration of a variety of steroids such as the androgenic steroids danazol or gestrinone and progestogens, or of compounds modulating the steroid hormone plasma levels like e.g. GnRH agonists and GnRH antagonists, whereby the administration is often associated a variety of serious side-effects.
Everything that has been said above in relation to the treatment of uterine leiomyomas and endometriosis equally applies to other benign gynaecological disorders, notably adenomyosis, functional menorrhagia and metrorrhagia. These benign gynaecological disorders are all estrogen sensitive and are treated in a comparable way as described herein before in relation to uterine leiomyomas and endometriosis. The available pharmaceutical treatments, however, suffer from the same major drawbacks, i.e. they have to be discontinued once the side-effects become more serious than the symptoms to be treated and symptoms reappear after discontinuation of the therapy.
Since the aforementioned malignant and benign pathologies are all 17β-estradiol dependent, a reduction of the endogenous 17β-estradiol concentration in the respective tissue will result in an impaired or reduced proliferation of 17β-estradiol responsive cells in said tissues. Therefore, selective inhibitors of the 17β-HSD1 enzyme are well suited for their use to impair endogenous productions of estrogens, in particular of 17β-estradiol, in myomas, endometriotic, adenomyotic and endometrial tissue. The application of a compound acting as selective inhibitor on the 17β-HSD1 which preferentially catalyses the reductive reaction will result in a lowered intracellular estradiol-concentration, since the reductive conversion of the estrone into the active estradiol is reduced or suppressed. Therefore, reversible or even irreversible inhibitors of the 17β-HSD1 may play a significant role in the prophylaxis and/or treatment of steroid-hormone, in particular 17β-estradiol, dependent disorders or diseases. Furthermore, the reversible or even irreversible inhibitors of the 17β-HSD1 should have no or only pure antagonistic binding activities to the estradiol receptor, in particular to the estrogen receptor a subtype, since agonistic binding of the estrogen receptor would lead to activation and subsequently to the proliferation and differentiation of the target cell. In contrast, antagonists of the estrogen receptor, so called anti-estrogens, bind competitively to the specific receptor protein thus preventing access of endogenous estrogens to their specific binding site.
At present it is described in the literature that several malignant disease as breast cancer, prostate carcinoma, ovarian cancer, uterine cancer, endometrial cancer and endometrial hyperplasia may be treated by the administration of a selective 17β-HSD1 inhibitor. Furthermore, a selective 17β-HSD1 inhibitor may be useful for the prevention of the aforementioned hormone-dependent cancers, especially breast cancer (e.g. WO 2004/080271). Furthermore, international patent application WO 03/017973 describes the use of a selective estrogen enzyme modulator (SEEM) in the manufacture of a drug delivery vehicle for intravaginal administration to treat or prevent a benign gynaecological disorder such as endometriosis in a mammalian female.
Another known target for estrogen deprivation is the steroid sulfatase enzyme (STS) (E.C. 3.1.6.2), which regulates the local production of estrogens and androgens from systemic precursors in several tissues [reviewed by Reed et al (2005)]. The enzyme catalyzes the hydrolysis of the sulfate esters of 3-hydroxy steroids, which are inactive transport or precursor forms of the active 3-hydroxy steroids. In particular, STS hydrolyzes in-active estron-sulfate into estrone, which is then further converted into the active estradiol by action of the above described 17β-HSD1 enzyme. Therefore, STS has a pivotal role in regulating the formation of biologically active steroids. The enzyme is widely distributed throughout the body and its action is implicated in physiological processes and pathological conditions, such as hormone-dependent tumors. STS expression is increased in breast tumors and has prognostic significance. The role of STS in supporting tumor growth of the breast and prostate prompted the development of potent STS inhibitors, since STS inhibitors are expected to block the local production and, consequently, to reduce the local levels of the hormones. Therefore, they are considered as potential therapeutic agents for the treatment of estrogen- and androgen-dependent disorders in general. Indications may range from cancers of the breast, endometrium and prostate to disorders of the pilosebaceous unit, e. g. acne, androgenetic alopecia, and hirsutism. Furthermore, STS inhibitors may be useful as immunosuppressive agents, and have been shown to enhance memory when delivered to the brain.
Acne is a polyetiological disease caused by the interplay of numerous factors, such as inheritance, sebum, hormones, and bacteria. The most important causative factor in acne is sebum production; in almost all acne patients sebaceous glands are larger and more sebum is produced than in persons with healthy skin. The development of the sebaceous gland and the extent of sebum production is controlled hormonally by androgens; therefore, androgens play a crucial role in the pathogenesis of acne. In man, there are two major sources supplying androgens to target tissues: (i) the gonades which secrete testosterone, (ii) the adrenals producing dehydroepiandrosterone (DHEA) which is secreted as the sulfate conjugate (DHEAS). Testosterone and DHEAS are both converted to the most active androgen, dihydrotestosterone (DHT), in the target tissue, e. g. in the skin. There is evidence that these pathways of local synthesis of DHT in the skin are more important than direct supply with active androgens from the circulation. Therefore, reduction of endogeneous levels of androgens in the target tissue by specific inhibitors should be of therapeutic benefit in acne and seborrhoea. Furthermore, it opens the perspective to treat these disorders through modulation of local androgen levels by topical treatment, rather than influencing circulating hormone levels by systemic therapies.
Androgenetic male alopecia is very common in the white races, accounting for about 95% of all types of alopecia. Male-pattern baldness is caused by an increased number of hair follicles in the scalp entering the telogen phase and by the telogen phase lasting longer. It is a genetically determined hair loss affected through androgens. Elevated serum DHEA but normal testosterone levels have been reported in balding men compared with non-balding controls, implying that target tissue androgen production is important in androgenetic alopecia.
Hirsutism is the pathological thickening and strengthening of the hair which is characterized by a masculine pattern of hair growth in children and women. Hirsutism is androgen induced, either by increased formation of androgens or by increased sensitivity of the hair follicle to androgens.
The presence of the STS enzyme in keratinocytes and in skin-derived fibroblasts has been described, and the potential use of STS inhibitors for the reduction of endogenous levels of steroid hormones in the skin was confirmed using known steroid sulfatase inhibitors, such as EMATE. Additionally, it has been described that inhibitors of placenta steroid sulfatase also inhibit steroid sulfatase in human keratinocyte or human skin-derived fibroblast cell lines. Therefore, STS inhibitors may be used to reduce androgen and estrogen levels in the skin, e.g. for the local treatment of androgen-dependent disorders of the pilosebaceous unit (such as acne, seborrhoea, androgenetic alopecia, hirsutism). STS inhibitors are also useful for the treatment of cancer, especially for the treatment of estrogen- and androgen-dependent cancers, such as cancer of the breast and endometrium, squamous cell carcinoma, and cancer of the prostata.
In addition, STS inhibitors may be useful for the prevention and treatment of further estrogen- or androgen-dependent diseases or disorders and/or diseases or disorders requiring the lowering of the endogeneous estrogen or androgen concentration in a generalized or tissue-specific manner, such as inflammatory and autoimmune diseases, e.g. rheumatoid arthritis, type I and II diabetes, systemic lupus erythematosus, multiple sclerosis, myastenia gravis, thyroiditis, vasculitis, ulcerative colitis, and Crohn's disease, psoriasis, contact dermatitis, graft versus host disease, eczema, asthma and organ rejection following transplantation. STS inhibitors are also useful for the enhancement of cognitive function, especially in the treatment of senile dementia, including Alzheimer's disease, by increasing the DHEAS levels in the central nervous system.
Several reversible or irreversible inhibitors of the 17β-HSD1 enzyme or of the steroid sulfatase of steroidal and even non-steroidal origin are already known from the literature. The characteristics of the inhibitory molecules of the 17β-HSD1 enzyme, which mainly have a substrate or cofactor-like core structure, have been reported in the literature [reviewed in: Poirier D. (2003)]. The characteristics and structure-activity relationship of known irreversible as well as reversible STS inhibitors have been reviewed in the literature [reviewed by Nussbaumer & Billich (2004) and (2003)]. Even dual inhibitors of the 17β-HSD1 enzyme and of the steroid sulfatase have been described in international patent application WO 02/32409.
The following compounds or compound classes have already been described as 17β-HSD1 inhibitors: For example, Tremblay and Poirier describe an estradiol derivative, 16-[carbamoyl-(bromo-methyl)-alkyl]-estradiol, and tested the same in respect of its inhibition of the estradiol formation catalysed by the enzyme 17β-HSD1 [Tremblay & Poirier (1998)]. Poirier and colleagues describe a 6β-thiaheptan-butyl-methyl-amide derivative of estradiol as a potent and selective inhibitor of the 17HSD1 enzyme [Poirier et al. (1998)]. Furthermore, Poirier and colleagues describe new derivatives of 17β-estradiol with long N-butyl, N-methyl alkylamide side chains of three different lengths (n=8, 10 or 12) at position 15, which might be potential inhibitors of the 17β-HSD1 enzyme [Poirier et al. (1991)]. Similar compounds were also disclosed within European patent application EP0367576. However, the biological activity of these compounds was only tested with regard to estrogen receptor binding affinity, estrogenic and anti-estrogenic activity [Poirier et al. (1996)], but not with regard to their ability to inhibit the 17β-HSD1 enzyme. In addition, Pelletier and Poirier describe novel 17β-estradiol derivatives with different bromo-alkyl side chains, which might be potential inhibitors of the 17β-HSD1 enzyme [Pelletier & Poirier (1996)]. Sam and colleagues describe several estradiol derivatives with a halogenated alkyl side chain in 16α or 17α position of the steroidal D-ring which possess 17β-HSD1 inhibiting properties [Sam et al. (1998)]. Furthermore, the finding that some anti-estrogens, such as tamoxifen, possess weak 17β-HSD1 inhibiting properties suggested that it may be possible to develop a potent 17β-HSD1 inhibitor that is also anti-estrogenic [reviewed in: Poirier D. (2003)]. Several of the aforementioned already known compounds also display anti-estrogenic properties (e.g. the 6β-thiaheptan-butyl-methyl-amide derivative of estradiol described by Poirier and colleagues [Poirier et al. (1998)]). None of the aforementioned compounds has been clinically used so far.
Furthermore, the international patent application WO 2004/085457 discloses a variety of estron derivatives with different substituents in C2, C3, C6, C16 and/or C17 position as potent 17β-HSD1 inhibitors. For some of the compounds it was shown that the substitution of steroid based 17β-HSD1 inhibitors at the C2 position with small hydrophobic groups renders the compounds less estrogenic and are favourable for 17β-HSD1 over 17β-HSD2 discrimination [Lawrence et al (2005)].
The international application WO 2005/047303, published on the filing date of the priority application of the present invention, discloses new 3, 15 substituted 17β-estradiol derivatives with different kind of side chains at position 15, which are potent and selective 17β-HSD1 inhibitors.
Additional compounds representing potential 17β-HSD1 inhibitors were disclosed within international applications WO 2006/003012 and WO 2006/003013 in the form of novel 2-substituted D-homo-estra-1,3,5(10)-trienes and novel 2-substituted estra-1, 3, 5(10)-trien-17-ones.
The synthesis of different B-, C- and D-ring substituted estradiol carboxylic esters was described by Labaree et al. [Labaree et al. (2003)]. However, these esters were only analysed with regard to their estrogenic potential. The related international patent application WO 2004/085345 discloses 15α substituted estradiol compounds bearing a —(CH2)m—CO—O—R side chain, wherein R is H, a C1-C5 alkyl group, optionally substituted with at least one halogen group, such as CH2CH2F, or other group (e.g. CH2CHF2, CH2CF3 or CF3 group); and m is from 0-5. These 15α estradiol esters are described as locally active estrogens without significant systemic action.
Furthermore, international application WO 2006/027347 discloses 15β substituted estradiol derivatives having selective estrogen receptor activity towards the estrogen receptor α-subtype.
Several compounds and compound classes have already been identified as STS inhibitors. They all share the common structural feature of an aromatic ring bearing a substituent that mimics the phenolic A-ring of the enzyme substrate, estrone-sulfate. On the development of steroidal inhibitors, a wide variety of chemical groups have been introduced at C3, of which the 3-0-sulfamate was found to be the most potent for the estrone molecule. The resulting compound, estrone-3-O-sulfamate (“EMATE”) led to the identification of the aryl-O-sulfamate structure as an active pharmacophore required for potent inhibition of STS (as disclosed in international patent application WO 93/05064). EMATE was shown to inhibit steroid sulfate activity in a time- and concentration-dependent manner and was active in vivo on oral administration. It was however revealed to be highly estrogenic which raised the need to design STS inhibitors devoid of agonist activity on the human estrogen receptor. For example, the recently published international patent application WO 2004/085459 discloses a variety of estron derivatives with different subsituents in C2, C3, C4 and/or C17 position as potent STS inhibitors.
Accordingly, there is still a need for the development of compounds which are suited for the treatment and/or prevention of steroid hormone dependent diseases or disorders such as breast cancer, endometriosis and uterine leiomyomas by selectively inhibiting the 17β-HSD1 enzyme and preferably additionally inhibiting the STS enzyme, while desirably failing to substantially inhibit other members of the 17β-HSD protein family or other catalysts of sex steroid degradation or activation. In particular, it is an aim of the present invention to develop selective inhibitors of the 17β-HSD1 enzyme, whereby in addition the compounds have no or only pure antagonistic binding affinities to the estrogen receptor (both subtypes α and β) and have favourably no residual activity on the 17β-HSD2 enyme. Furthermore, an increased metabolic stability of the compounds, in particular of the C17 keto position of the steroidal core, would be desirable, in order to prevent conversion of the estron to the respective estradiol derivative, which shows less inhibitory potential on the 17β-HSD1 enzyme.